Low loss optical material

ABSTRACT

Storage stable, UV curable, NIR transparent, polycondensates and methods for the production thereof by condensation of one or more silanediols of formula (I) and/or derived precondensates thereof  
                 
 
     with one or more silanes of formula (II) and/or derived precondensates thereof  
                 
 
     At least one of the aromatic groups Ar 1  or Ar 2  bears a cross-linkable functional group. The polycondensates are curable by crosslinking.

FIELD OF THE INVENTION

[0001] The invention relates to improvements in the performance of lowloss optical materials resulting from chemical modification, and toimproved polymeric siloxanes.

BACKGROUND OF THE INVENTION

[0002] Organically modified siloxanes (alternating Si—O backbonedpolymers) have a broad range of applications. In particular, they havegood light transmission properties which make them ideal targets for usein optical materials such as optical fibres and devices. They alsogenerally possess good adhesion as well as mechanical and chemicalstability over an extended temperature range.

[0003] Siloxane polymers can be divided into two broad classes—

[0004] (i) polysiloxanes prepared by the sol-gel route and

[0005] (ii) standard siloxane polymers of the polydiorganosiloxane type.

[0006] Polysiloxanes prepared by the sol-gel route are sometimesreferred to as ORMOSIL (ORganically MOdified SILicates), ORMOCER(ORganically MOdified CERamics) or inorganic-organic hybrid polymers.These are formed from alkoxysilanes which are normally hydrolysed in thepresence of base or acid to yield the corresponding silanol which thenundergoes condensation to give a highly cross-linked polysiloxane.

[0007] Problematically, these polymers are difficult to process due totheir high viscosity. While the condensation processes can be sloweddown somewhat to assist in processing, there is always a tendency forsuch materials to condense so problems due to high viscosity areinevitable.

[0008] A further consequence of this unavoidable condensation is theformation of microgels. These microgels make filtration difficult,particularly the passage through 0.2 μm filters, a step which isessential in preparing optical materials to avoid scattering losses.

[0009] WO 01/04186 discloses a method for the condensation of diarylsilanediols with trialkoxy silanes. This method produces apolycondensate with the concomitant elimination of alcohol, according tothe following scheme:

[0010] n Ar₂Si(OH)₂+n RSi(OR′)₃→Polycondensate+2n R′OH

[0011] This synthetic route avoids the presence of large numbers of OHgroups which have a high near IR absorption (3500 cm⁻¹) that impactsnegatively upon optical transparency at 1550 nm. Uncondensed Si—OHgroups can also continue a slow reaction over the service life of thepolymeric material and lead to cracking and loss of adhesion.

[0012] It is desirable to cross-link polymer chains to provide greaterchemical stability for the polymer matrix and more importantly to modifythe physical properties of the polymer. The most important of these isthe ability to cross-link to modify rheology, which in practical termsrepresents the ability to cure the material from a relatively lowviscosity workable polymer to a polymer matrix with sufficientmechanical rigidity to allow use in applications such as opticaldevices.

[0013] WO 01/04186 discloses a number of cross-linking groups such asepoxy and acrylate groups which are pendant from the trialkoxy silane,RSi(OR′)₃. There was little or no attention paid to groups which mightadvantageously provide controlled cross-linking based around the silanediol moiety.

[0014] The trialkoxy silane RSi(OR′)₃ component is typically used forintroducing functionality into the polymer, with the diaryl silane diolhaving two reactive OH groups and two “blocking” aryl moieties.

[0015] The approach disclosed in WO 01/04186 means that, for analternating polymer, 50% of monomer units—the trialkoxy silaneunits—have to bear all the desired functionalities, for example,cross-linking, refractive index tuning and fluorination for loweroptical loss. This approach is limiting in terms of the syntheticapproaches which can be pursued.

[0016] It is an object of the present invention to providepolycondensates and polymeric matrices based on the above syntheticroute, but which are more readily controlled in terms of structure andfunctionality.

SUMMARY OF THE INVENTION

[0017] According to a first aspect the invention provides a storagestable, UV curable, NIR transparent, polycondensate produced bycondensation of one or more silanediols of formula (I) and/or derivedprecondensates thereof

[0018] with one or more silanes of formula (II) and/or derivedprecondensates thereof

[0019] wherein Ar¹ and Ar² are independently a group with 5 to 20 carbonatoms and at least one aromatic or heteroaromatic group and at least oneof Ar¹ and Ar² bears a cross-linkable functional group; and

[0020] R¹, R², R³ and R⁴ are independently alkyl, aralkyl or aryl withup to 20 carbon atoms.

[0021] Preferably in the present invention the ratio of formula (I) andformula (II) is 1:1.

[0022] The invention also provides a polycondensate of the structure

[0023] wherein

[0024] Ar¹ and Ar² are independently a group with 5 to 20 carbon atomsand at least one aromatic or heteroaromatic group and at least one ofAr¹ and Ar² bears a cross-linkable group;

[0025] R¹ and R² are independently alkyl, aralkyl or aryl with up to 20carbon atoms; and q is at least 1.

[0026] According to a second aspect the invention provides a method ofproduction of a polycondensate including the step of condensing one ormore silanediols of formula (I) and/or a derived precondensates thereof

[0027] with one or more silanes of formula (II) and/or derivedprecondensates thereof

[0028] wherein Ar¹ and Ar² are independently a group with 5 to 20 carbonatoms and at least one aromatic or heteroaromatic group and at least oneof Ar¹ and Ar² bears a cross-linkable functional group; and

[0029] R¹, R², R³ and R⁴ are independently alkyl, aralkyl or aryl withup to 20 carbon atoms.

[0030] Preferably the molar ratio of formula (I): formula(II) is 1:1.

[0031] The invention also provides a method of preparing apolycondensate of the structure

[0032] including the step of condensing one or more silanediols offormula (I) and/or derived precondensates thereof

[0033] with one or more silanes of formula (II) and/or derivedprecondensates thereof

[0034] wherein Ar¹ and Ar² are independently a group with 5 to 20 carbonatoms and at least one aromatic or heteroaromatic group and at least oneof Ar¹ and Ar² bears a cross-linkable functional group;

[0035] R¹, R², R³ and R⁴ are independently alkyl, aralkyl or aryl withup to 20 carbon atoms; and q is at least 1.

[0036] According to a third aspect the invention provides a monomer offormula (I)

[0037] when used for the preparation of a storage stable, UV curable,NIR transparent, polycondensate

[0038] wherein Ar¹ and Ar² are independently a group with 5 to 20 carbonatoms and at least one aromatic or heteroaromatic group and at least oneof Ar¹ and Ar² bears a cross-linkable functional group.

[0039] According to a fourth aspect the invention provides a curedpolycondensate prepared by curing a polycondensate according to thefirst aspect, or curing a polycondensate produced according to thesecond aspect, or curing a polycondensate which includes at least onemonomer of the third aspect.

[0040] In the above compounds and methods, it is preferable if at leastone of Ar¹ and Ar² is a moiety of the type

[0041] In alternative embodiments, at least one of Ar¹ and Ar² issubstituted with an epoxy group or a double bond, for instance, anacrylate.

[0042] In alternative preferred embodiments, at least one of Ar¹ and Ar²is a moiety of the type

[0043] where L is a connecting group which is selected from alkyl,aralkyl, or ether; n is 0-5; and

[0044] R¹, R², R³ and R⁴ are independently alkyl, aralkyl or aryl withup to 20 carbon atoms.

[0045] Preferably L is selected from the group consisting of: —CH₂—,—(OCH₂)— and —(OCH₂CH₂)—.

[0046] Preferably at least one of Ar¹, Ar², R¹, R², R³ and R⁴ bears atleast one fluorine as a substituent.

[0047] In alternative embodiments, at least one of Ar¹, Ar², R¹, R², R³and R⁴ additionally bears at least one substituent selected from thegroup consisting of —OH, —SH and —NH₂.

[0048] In preferred embodiments, at least one of Ar¹ and Ar² is selectedfrom the group consisting of:

[0049] In one highly preferred embodiment, Ar¹ is phenyl and Ar² is4-styryl. Preferably R¹ is selected from the group consisting ofCF₃(CH₂)₂—, CF₃(CF₂)₅(CH₂)₂—, CH₃(CH₂)₂—, —CH₃ and phenyl.

[0050] Preferably R², R³ and R⁴ are independently selected from thegroup consisting of methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyland octyl.

[0051] In alternative preferred embodiments, up to 90 mol % of thesilane of formula (II) is replaced with a co-condensable compound ofboron, aluminum, silicon, germanium, titanium or zirconium.

[0052] In another alternative embodiment, up to 90 mol % of formula (I)is substituted with a non-cross-linkable compound, for example diphenylsilane diol.

[0053] It is preferred if the polycondensates according the presentinvention are capable of being photo-structured in layers up to 150 μmin thickness.

[0054] In another aspect, the present invention provides a curedcondensate and a method of preparing a cured polycondensate includingthe step of treating a polycondensate of the present invention with acuring agent.

[0055] In highly preferred embodiments the curing agent is light. Aphotoinitiator may be added.

[0056] Preferably, the light is UV light and the photoinitiator isselected from the group consisting of: 1-hydroxycyclohexylphenyl ketone,benzophenone, 2-chlorothioxanthone, 2-methylthioxanthone,2-iso-propylthioxanthone, benzoin, 4,4′-dimethoxybenzoin and mixturesthereof.

[0057] In an alternative preferred embodiment, the light is visiblelight and the photoinitiator may be, for example, camphorquinone.

[0058] In further alternative embodiments, other initiators may beadded. These may be for example dibenzoyl peroxide, t-butyl perbenzoateand azobisisobutyronitrile.

[0059] Furthermore the resin can also be thermally cured using noinitiator whatsoever. The curing temperature is between 80-250° C. andmore preferably between 170-210° C.

DETAILED DESCRIPTION OF THE INVENTION

[0060] The storage stable, UV curable, NIR transparent, polycondensateof the present invention is produced by condensation of one or moresilanediols of formula (I) and/or derived precondensates thereof

[0061] with one or more silanes of formula (II) and/or derivedprecondensates thereof

[0062] wherein Ar¹ and Ar² are independently a group with 5 to 20 carbonatoms and at least one aromatic or heteroaromatic group and at least oneof Ar¹ and Ar² bears a cross-linkable functional group; and

[0063] R¹, R², R³ and R⁴ are independently alkyl, aralkyl or aryl withup to 20 carbon atoms.

[0064] Preferably, the molar ratio of formula (I) to formula (II) is1:1.

[0065] The resultant polycondensate may be defined either in terms ofthe precondensate compounds used, or in terms of the structure of thepolycondensate, which may be defined by the following structure

[0066] wherein

[0067] Ar¹ and Ar² are independently a group with 5 to 20 carbon atomsand at least one aromatic or heteroaromatic group and at least one ofAr¹ and Ar² bears a cross-linkable group;

[0068] R¹ and R² are independently alkyl, aralkyl or aryl with up to 20carbon atoms; and q is at least 1.

[0069] In the present invention, the aromatic groups Ar¹ and/or Ar² bearcross-linking functionalities, most commonly a double bond, such as thatin a styrene or acrylate (where they are more reactive by conjugation),or epoxides. Each aromatic group may also bear more than onecross-linkable group, although it will be appreciated by those skilledin the art that precursors of such compounds may be difficult to processfrom a synthetic point of view.

[0070] The cross-linking group may be directly on the aromatic group, orany or all of the silicon atoms and the aromatic group and cross-linkingfunctionality may be spaced apart with connecting groups, which may beinert or reactive as desired.

[0071] The cross linking group may be attached to the aromatic group byany intervening moiety.

[0072] Substitution of a hydrogen on any of the components with fluorinemay take place in order to enhance the optical properties of thepolycondensate and subsequently cured matrix.

[0073] Other reactive species, such as —OH, —SH and —NH₂ may also bepresent on one or more of the substituents, to facilitate additionalchemistry of the matrix, polycondensate, oligomeric or monomeric speciesas desired.

[0074] In one highly preferred embodiment of the present invention, Ar¹is phenyl and Ar² is 4-styryl. Preferably, Ar¹ and Ar² are not both4-styryl.

[0075] In another alternative embodiment, up to 90 mol % of formula (I)is substituted with a non-cross-linkable compound, for example diphenylsilane diol.

[0076] As mentioned above, by placing the cross-linking function on theAr₂Si(OH)₂ compound, the other 50% of monomer units (those of formulaII) have one less burden to carry, leaving more of them available forother functions.

[0077] In this present improvement, the cross-linkable unit is placed onthe Ar₂Si(OH)₂ compound, obviating the need for the RSi(OR′)₃ compoundto have any cross-linkable groups.

[0078] Also, having the cross-linking function on the Ar₂Si(OH)₂compound generally means that a more thermally stable polymer results.For example, the use of styrene groups, highly preferred in the presentinvention, rather than the acrylate groups specifically recited andexemplified in WO 01/04186 results in a polymer in which the cross-linksare via polystyrene type bonds. It will be appreciated by those skilledin the art that such bonds are more thermally stable that those in thecorresponding polyacrylate cross-linked polymer.

[0079] The polycondensates of the present invention are described hereinwith reference to idealised structural representations, ie they areshown as alternating units. Those skilled in the art will appreciatethat, in reality, the polymers themselves are statistical polymers andas such, will be unlikely to have only repeating units. It is notnecessary that the monomer precursors are present in a 1:1 ratioalthough this is preferred.

[0080] Because the polymers of the present invention rely oncross-linking through the aryl group of the diaryl silane diol, theRSi(OR′)₃ component can be varied or substituted for any co-condensableequivalent compound. Examples of alternative compounds have beenprovided in WO 01/04186. For production of the polymers of the presentinvention, at least a portion (up to 90%) of RSi(OR′)₃ can be replacedby one or more co-condensable compounds of boron or aluminum of generalformula (III). These substitutions may have the advantage of increasingchemical stability and mechanical hardness.

M(OR″)₃  (III)

[0081] The groups R″ are identical or different, M signifies boron oraluminum and R″ represents an alkyl group with 1 to 4 carbon atoms. Inthe general formula (III), all three alkoxy groups can condense withcompounds of general formula (I), so that only ⅔ of the molar quantityis required. The replacement compounds can be quite highly branchedbefore cross-linking. Examples of compounds of general formula (III) areAl(OCH₃)₃, Al(OC₂H₅)₃, Al(O-n-C₃H₇)₃, Al(O-i-C₃H₇)₃, Al(O-n-C₄H₉)₃,Al(O-i-C₄H₉)₃, Al(O-s-C₄H₉)₃, B(O-n-C₄H₉)₃, B(O-t-C₄H₉)₃, B(O-n-C₃H₇)₃,B(O-i-C₃H₇)₃, B(OCH₃)₃ and B(OC₂H₅)₃.

[0082] Alternatively, at least a portion (up to 90%) of RSi(OR)₃ can bereplaced by one or more co-condensable compounds of silicon, germanium,titanium or zirconium of general formula (IV).

M′(OR″)₄  (IV)

[0083] The groups R″ are identical or different, M′ signifies silicon,germanium titanium or zirconium and R″ represents an alkyl group with 1to 4 carbon atoms. In the general formula (IV), all four alkoxy groupscan condense with compounds of general formula (I), so two molecules ofcompound (II) may be replaced by one molecule of compound (IV). Examplesof compounds of general formula (IV) include Si(OCH₃)₄, Si(OC₂H₅)₄,Si(O-n-C₃H₇)₄, Si(O-i-C₃H₇)₄, Si(O-n-C₄H₉)₄, Si(O-i-C₄H₉)₄,Si(O-s-C₄H₉)₄, Ge(OCH₃)₄, Ge(OC₂H₅)₄, Ge(O-n-C₃H₇)₄, Ge(O-i-C₃H₇)₄,Ge(O-n-C₄H₉)₄, Ge(O-i-C₄H₉)₄, Ge(O-s-C₄H₉)₄, Ti(OCH₃)₄, Ti(OC₂H₅)₄,Ti(O-n-C₃H₇)₄, Ti(O-i-C₃H₇)₄, Ti(O-n-C₄H₉)₄, Ti(O-i-C₄H₉)₄,Ti(O-s-C₄H₉)₄, Zr(OCH₃)₄, Zr(OC₂H₅)₄, Zr(O-n-C₃H₇)₄, Zr(O-i-C₃H₇)₄,Zr(O-n-C₄H₉)₄, Zr(O-i-C₄H₉)₄ and Zr(O-s-C₄H₉)₄.

[0084] The present invention allows for the substitution of these groupsinto the polycondensate without the requirement that they also providecross-linking functionality, because this is provided via thefunctionalities pendant on the aromatic ring.

[0085] By substituting the compounds of general formula (II) bycompounds of general formula (III) or (IV), the refractive index andoptical attenuation of the resultant polycondensate can be tuned to aspecific application. For example at certain wavelengths,alkyl-substituted components cause a reduction in refractive index whilesimultaneously increasing the attenuation where aryl-substitutedcomponents cause an increase in refractive index without significantlyincreasing the attenuation of the inventive material. Fluorination, bycontrast, decreases both the refractive index and the attenuation of theinventive polycondensates.

[0086] Other resins, oligomers or monomers or particulate matter orother functional material may be added to the reaction mixture to modifythe physical (refractive index), mechanical (hardness, thermal expansionprofile) or chemical (introduction of reactive moieties) properties ofthe resulting polycondensate.

[0087] Other non-cross-linkable moieties, for example diphenyl silanediol, may be added to the mixture prior to condensation. This can beadded to statistically space the number of cross-linking units on thechain. These units are typically less expensive than cross-linkableunits and may be used where sufficient rigidity can be achieved withoutcross-linking of all the potential cross-linking units in thepolycondensate. For example, if sufficient hardness is achieved when 10%of the polymer groups are cross-linked, then up to 90% of thecross-linkable groups may be replaced with non-cross-linkable groups.These non-cross-linkable groups can also be used to introduce additionalfunctionality into the polycondensate.

[0088] To initiate or accelerate the condensation, Lewis or Bronsteadbases can be added. Some examples are amines, e.g. N-methyl imidazole,benzyldimethylamine, triethylamine, ammonium fluoride or one or morealkaline earth hydroxides. The alkaline earth hydroxide barium hydroxideis particularly preferred. Insoluble bases are recommended because theyhave the advantage that they can be readily removed from the mixture byfiltration after condensation. Aluminum or zirconium alkoxides can beused in place of the abovementioned bases for the condensation.

[0089] The polycondensates of the present invention have good storagestability, ie they do not gel or cross-link when maintained in theappropriate conditions (ie away from polymerisation sources).

[0090] The polycondensates of the present invention are UV curable andtransparent in the NIR, especially at the wavelengths of 1310 nm and1550 nm which are critical for optical applications. Curing, i.e.cross-linking proceeds with little associated shrinkage, meaningcracking in the bulk cured material can be avoided (cracking causesdiscontinuities in the material, making it unsuitable for optical datatransmission).

[0091] The polycondensates of the present invention arephoto-structurable in layers of thickness up to 150 μm without loss ofquality, making them suitable for application as photoresists, negativeresists, dielectrics, light guides, transparent materials, or asphoto-structurable materials.

[0092] Before curing and further processing, a solvent can be added tothe polycondensate if desired and, if necessary, a suitable initiatorcan be added. In the curing processes, the C═C double bonds or the epoxygroups are linked together, many from different polycondensate chains,and the organic polymer matrix is constructed. Because of the relativelyhigh molecular weight of the inventive polycondensates, curing proceedswith only minimal shrinkage.

[0093] It is also possible to add further polymerisable componentsbefore curing, for example, acrylates or methacrylates, or styrenecompounds (to space polymer chains) where the polymerisation proceedsacross the C═C double bonds, or compounds containing ring systems thatare polymerisable by cationic ring opening.

[0094] Photoinitiators or thermal initiators may be added to increasethe rate of curing. Commercially available photoinitiators include1-hydroxycyclohexylphenyl ketone, benzophenone, 2-chlorothioxanthone,2-methylthioxanthone, 2-iso-propylthioxanthone, benzoin,4,4′-dimethoxybenzoin etc. For curing with visible light, the initiatormay be for example camphorquinone.

[0095] For thermal initiators, organic peroxides in the form ofperoxides (e.g. dibenzoyl peroxide), peroxydicarbonates, peresters(t-butyl perbenzoate), perketals, hydroperoxides may also be used. AIBN(azobisisobutyronitrile) may also be used.

[0096] Radiation cure, for example by gamma rays or electron beam, isalso possible.

EXAMPLES

[0097] The invention will be further illustrated by the followingexamples which are intended to be illustrative, but not limiting.

[0098] Sample Preparation and Measurement.

[0099] All resins described in Examples 1-7 were filtered through a 0.2μm filter after preparation.

[0100] The optical loss was measured with a SHIMADZU UV-VIS-NIRspectrophotometer (UV-3101 PC) using a 0.5 cm quartz cuvette. Since theresins are colourless the absorption was calibrated using the zeroabsorption area ≦700 nm as baseline. The absorption spectrum from theresin was measured from 3200 nm-200 nm. The lowest absorption value(usually the absorption between 700 and 550 nm is a straight line ifthere is no scattering as a result of particles and if the resin iscolourless) is set as 0 absorption. The loss in dB/cm is calculated fromthe optical density of the resin at 1310 and 1550 nm, multiplied by 10and divided by the thickness of the cuvette in cm (whereas the opticaldensity equals the log to the base 10 of the reciprocal of thetransmittance). The loss was estimated from the un-cured resin only.

[0101] The refractive index was estimated by a standard refractometerusing daylight as the light source.

[0102] Synthesis

[0103] Synthesis of 4-vinyldiphenylsilanediol

[0104] A 500 ml three neck round bottom flask equipped with a nitrogeninlet, stirrer and condenser was charged with 19.00 g (0.78 mol)magnesium turnings. Under a nitrogen atmosphere 125 ml of anhydrous THFand 125 ml of anhydrous diethylether were added followed by 98.75 g(0.71 mol) of 4-chlorostyrene. The mixture was kept at 50° C. for 16 h,to form the Grignard solution.

[0105] A two liter three neck round bottom flask equipped with anitrogen inlet, dropping funnel and condenser was charged with 423.86g(2.14 mol) phenyltrimethoxysilane. The system was purged with nitrogenand the Grignard solution was transferred into the dropping funnel. Theflask was heated to 50° C., then the Grignard solution was added over aperiod of 40 min and kept at this temperature for an additional 2 h.

[0106] The reaction was allowed to cool to room temperature, 1 liter ofpetroleum ether was added, the precipitated salt was separated byfiltration and the solvent was distilled off.

[0107] The product was distilled under reduced pressure using 2.00g of2-methyl-1,4-naphthoquinone and 2.00g N,N-diphenylhydroxylamine aspolymerisation inhibitors.

[0108] Yield: 64%=122.73 g (0.45 mol) 4-vinyldiphenyldimethoxysilane(bp.112-118° C.@2.5*10⁻² mbar).

[0109] 160.00 g (0.59 mol) 4-vinyldiphenyldimethoxysilane was dissolvedin 400 ml isopropanol and 125 ml 1 M acetic acid was added. The solutionwas stirred at room temperature for 48 h and 300 ml of the solvents weredistilled off. The solution was neutralised with saturated NaHCO₃ andextracted twice with 200 ml ethyl acetate. The combined organic layerwas dried over MgSO₄ and the solvents distilled off under reducedpressure. The crude product was ground and extracted with petroleumether in a Soxhlet apparatus.

[0110] Yield: 63%=89.87 g (0.371 mol) 4-vinyldiphenylsilanediol.

[0111] Synthesis of Resins with the General Structure

Example 1 R⁵, R⁶═CF₃(CH₂)₂—, R⁷═H

[0112] 3.63g (15 mmol) 4-vinyldiphenylsilanediol (VDPS), 3.25g (15 mmol)of diphenylsilanediol (DPS) and 6.55 g (30 mmol)3,3,3-trifluoropropyltrimethoxysilane were placed in a 50 ml roundbottom flask equipped with a magnetic stirrer bar and condenser. 0.015g(0.06 mmol) Ba(OH)₂.H₂O was added and the flask was placed immediatelyin an 80° C. oilbath. A condenser was placed on the flask and thereaction mixture was stirred thoroughly.

[0113] After a few minutes the solution became clear and reflux ofmethanol started. After 15 min at 80° C. the flask was transferred to arotary evaporator and the solvent distilled off at 80° C. under 640 mbarpressure for 40 min. Then the pressure was reduced to 10 mbar and theresin kept at 80° C. for an additional 1 h.

[0114] The product was filtered through a 0.2 μm filter and used withoutany further purification.

[0115] Selected physical properties:

[0116] Refractive index: n_(D) ²² 1.5153

[0117] Optical loss: 0.15 dB/cm@1310 nm, 0.30 dB/cm@1550 nm

Example 2 R⁵, R⁶═CF₃(CF₂)₅(CH₂)₂—, R⁷═H

[0118] 9.69g (40 mmol) VDPS

[0119] 8.65g (40 mmol) DPS

[0120] 37.46g (80 mmol) 1H,1H,2H,2H-Perfluorooctyltrimethoxysilane

[0121] 50 mg (0.26 mmol) Ba(OH)₂.H₂O

[0122] Synthetic procedure was the same as for example 1.

[0123] Selected physical properties:

[0124] Refractive index: n_(D) ²² 1.4510

[0125] Optical loss: 0.13 dB/cm@11310 nm, 0.25 dB/cm@ 1550 nm

Example 3 R⁵, R⁶═CH₃(CH₂)₂—, R═H

[0126] 3.63g (15 mmol) VDPS

[0127] 3.25g (15 mmol) DPS

[0128] 4.94g (30 mmol) n-propyltrimethoxysilane

[0129] 14 mg (0.06 mmol) Ba(OH)₂.H₂O

[0130] Synthetic procedure was the same as for example 1.

[0131] Selected physical properties:

[0132] Refractive index: n_(D) ²² 1.5481

[0133] Optical loss: 0.17 dB/cm@1310 nm, 0.34 dB/cm@1550 nm

Example 4 R⁵, R⁶═CH₃—, R⁷═H

[0134] 4.85g (20 mmol) VDPS

[0135] 4.32g (20 mmol) DPS

[0136] 5.45g (40 mmol) methyltrimethoxysilane

[0137] 25 mg (0.08 mmol) Ba(OH)₂.H₂O

[0138] Synthetic procedure was the same as for example 1.

[0139] Selected physical properties:

[0140] Refractive index: n_(D) ²² 1.5609

[0141] Optical loss: 0.17 dB/cm@1310 nm, 0.43 dB/cm@1550 nm

Example 5 R⁵═CF₃(CF₂)₅(CH₂)₂—, R⁶═Ph, R⁷═H

[0142] 2.42g (10 mmol) VDPS

[0143] 2.16g (10 mmol) DPS

[0144] 4.68g (10 mmol) 1H,1H,2H,2H-perfluorooctyltrimethoxysilane

[0145] 1.98g (10 mmol) phenyltrimethoxysilane

[0146] 8 mg (0.04 mmol) Ba(OH)₂.H₂O

[0147] Synthetic procedure was the same as for example 1.

[0148] Selected physical properties:

[0149] Refractive index: n_(D) ²² 1.4980

[0150] Optical loss: 0.13 dB/cm@1310 nm, 0.25 dB/cm@1550 nm

Example 6 R⁵, R⁶═CF₃(CH₂)₂—, R⁷═H₂C═CH—

[0151] 5.00g (21 mmol) VDPS

[0152] 4.50g (21 mmol) 3,3,3-trifluorotrimethoxysilane

[0153] 8 mg (0.04 mmol) Ba(OH)₂.H₂O

[0154] Synthetic procedure was the same as for example 1.

[0155] Selected physical properties:

[0156] Refractive index: n_(D) ²² 1.5246

[0157] Optical loss: 0.16 dB/cm@11310 nm, 0.35 dB/cm@1550 nm

Example 7 R⁵, R⁶═Ph, R⁷═H₂C═CH—

[0158] 7.27g (30 mmol) VDPS

[0159] 5.95g (30 mmol) phenyltrimethoxysilane

[0160] 25 mg (0.12 mmol) Ba(OH)₂.H₂O

[0161] Synthetic procedure was the same as for example 1.

[0162] Selected physical properties:

[0163] Refractive index:n_(D) ²⁵ 1.5953

[0164] Optical loss: 0.19 dB/cm@1310 nm, 0.32 dB/cm@1550 nm

[0165] Curing

[0166] The material produced in example 1 was mixed with 2% Irgacure1000as photoinitiator and stirred under the exclusion of light for 24 hours.2 ml of this mixture was spun onto a 10 cm Si-wafer at 4000 rpm for 60s.The wafer was exposed to UV-light using a Hg arc lamp with 8 mW/cm²intensity for 60s under a nitrogen atmosphere. The thickness of the filmwas 12.8 μm.

[0167] The invention has been described by reference to certainpreferred embodiments; however, it should be understood that it may beembodied in other specific forms or variations thereof without departingfrom its spirit or essential characteristics. The embodiments describedabove are therefore considered to be illustrative in all respects andnot restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description.

1. A storage stable, UV curable, NIR transparent, polycondensateproduced by condensation of one or more silanediols of formula (I)and/or derived precondensates thereof

with one or more silanes of formula (II) and/or derived precondensatesthereof

wherein Ar¹ and Ar² are independently a group with 5 to 20 carbon atomsand at least one aromatic or heteroaromatic group and at least one ofAr¹ and Ar² bears a cross-linkable functional group; and R¹, R², R³ andR⁴ are independently alkyl, aralkyl or aryl with up to 20 carbon atoms.2. A polycondensate according to claim 1 wherein at least one of Ar¹ andAr² is a moiety of the type


3. A polycondensate according to claim 1 wherein the molar ratio offormula (I): formula (II) is 1:1.
 4. A polycondensate according to claim1 wherein at least one of Ar¹ and Ar² is substituted with an epoxy groupor a double bond.
 5. A polycondensate according to claim 4 wherein atleast one of Ar¹ and Ar² is substituted with an acrylate.
 6. Apolycondensate according to claim 1 wherein at least one of Ar¹ and Ar²is a moiety of the type

where L is a connecting group selected from alkyl, aralkyl, or ether;and n is 0-5.
 7. A polycondensate according to claim 6 wherein L isselected from the group consisting of: —CH₂—, —(OCH₂)— and —(OCH₂CH₂)—.8. A polycondensate according to claim 1 wherein at least one of Ar¹,Ar², R¹, R², R³ and R⁴ bears at least one fluorine as a substituent. 9.A polycondensate according to claim 1 wherein at least one of Ar¹, Ar²,R¹, R², R³ and R⁴ bears at least one substituent selected from the groupconsisting of —OH, —SH and —NH_(2.)
 10. A polycondensate according toclaim 1 wherein at least one of Ar¹ and Ar² is selected from the groupconsisting of:


11. A polycondensate according to claim 1 wherein Ar¹ is phenyl and Ar²is 4-styryl.
 12. A polycondensate according to claim 1 wherein R¹ isselected from the group consisting of CF₃(CH₂)₂—, CF₃(CF₂)₅(CH₂)₂—,CH₃(CH₂)₂—, —CH₃ and phenyl.
 13. A polycondensate according to claim 1wherein R², R³ and R⁴ are independently selected from the groupconsisting of methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl andoctyl.
 14. A polycondensate according to claim 1 wherein up to 90 mol %of the silane of formula (II) is replaced with a co-condensable compoundof boron, aluminum, silicon, germanium, titanium or zirconium.
 15. Apolycondensate according to claim 1 wherein up to 90 mol % of formula(I) is substituted with a non-cross-linkable compound.
 16. Apolycondensate according to claim 15 wherein the non-cross-linkablecompound is diphenyl silane diol.
 17. A method of production of apolycondensate by including the step of condensing one or moresilanediols of formula (I) and/or derived precondensates thereof

with one or more silanes of formula (II) and/or derived precondensatesthereof

wherein Ar¹ and Ar² are independently a group with 5 to 20 carbon atomsand at least one aromatic or heteroaromatic group and at least one ofAr¹ and Ar² bears a cross-linkable functional group; and R¹, R², R³ andR⁴ are independently alkyl, aralkyl or aryl with up to 20 carbon atoms.18. A monomer of formula (I)

when used for the preparation of a storage stable, UV curable, NIRtransparent, polycondensate wherein Ar¹ and Ar² are independently agroup with 5 to 20 carbon atoms and at least one aromatic orheteroaromatic group and at least one of Ar¹ and Ar² bears across-linkable functional group.
 19. A cured polycondensate prepared bycuring a polycondensate including at least one monomer of formula (I).20. A cured polycondensate prepared by curing a polycondensate accordingto claim
 1. 21. A method of preparing a cured polycondensate includingthe step of treating a polycondensate according to claim 1 with a curingagent.
 22. A method according to claim 21 wherein the curing agent islight.
 23. A method according to claim 22 wherein the curing agent islight and a photoinitiator is added.
 24. A method according to claim 23wherein the light is UV light and the photoinitiator is selected fromthe group consisting of: 1-hydroxycyclohexylphenyl ketone, benzophenone,2-chlorothioxanthone, 2-methylthioxanthone, 2-iso-propylthioxanthone,benzoin, 4,4′-dimethoxybenzoin and mixtures thereof.
 25. A methodaccording to claim 23 wherein the light is visible light and thephotoinitiator is camphorquinone.
 26. A method according to claim 21wherein an initiator is added.
 27. A method according to claim 26wherein the initiator is dibenzoyl peroxide, t-butyl perbenzoate orazobisisobutyronitrile.
 28. A polycondensate of the structure

wherein Ar¹ and Ar² are independently a group with 5 to 20 carbon atomsand at least one aromatic or heteroaromatic group and at least one ofAr¹ and Ar² bears a cross-linkable group; R¹ and R² are independentlyalkyl, aralkyl or aryl with up to 20 carbon atoms; and q is at least 1.29. A polycondensate according to claim 28 wherein at least one of Ar¹and Ar² is a moiety of the type


30. A polycondensate according to claim 28 wherein at least one of Ar¹and Ar² is substituted with an epoxy group or a double bond.
 31. Apolycondensate according to claim 30 wherein at least one of Ar¹ and Ar²is substituted with an acrylate.
 32. A polycondensate according to claim28 wherein at least one of Ar¹ and Ar² is a moiety of the type

where L is a connecting group is selected from alkyl, aralkyl, or ether;and n is 0-5.
 33. A polycondensate according to claim 32 wherein L isselected from the group consisting of: —CH₂—, —(OCH₂)— and —(OCH₂CH₂)—.34. A polycondensate according to claim 28 wherein at least one of Ar¹,Ar², R¹ and R² bears fluorine as a substituent.
 35. A polycondensateaccording to claim 28 wherein at least one of Ar¹, Ar², R¹ and R² bearsat least one substituent selected from the group consisting of —OH, —SHand —NH₂.
 36. A polycondensate according to claim 28 wherein at leastone of Ar¹ and Ar² is selected from


37. A polycondensate according to claim 28 wherein Ar¹ is phenyl and Ar²is 4-styryl.
 38. A polycondensate according to claim 28 wherein R¹ isselected from the group consisting of CF₃(CH₂)₂—, CF₃(CF₂)₅(CH₂)₂—,CH₃(CH₂)₂—, —CH₃ and phenyl.
 39. A polycondensate according to claim 28wherein R² is selected from the group consisting of methyl, ethyl,propyl, butyl, pentyl, hexyl, heptyl and octyl.
 40. A polycondensateaccording to claim 28 wherein up to 90 mol % of silane of formula (II)is replaced with a co-condensable compound of boron, aluminum, silicon,germanium, titanium or zirconium.
 41. A polycondensate according toclaim 28 wherein up to 90 mol % of formula (I) is substituted with anon-cross-linkable compound.
 42. A polycondensate according to claim 41wherein the non-cross-linkable compound is diphenyl silane diol.
 43. Amethod of preparing a polycondensate of the structure

including the step of condensing one or more silanediols of formula (I)and/or deriyed precondensates thereof

with one or more silanes of formula (II) and/or derived precondensatesthereof

wherein Ar¹ and Ar² are independently a group with 5 to 20 carbon atomsand at least one aromatic or heteroaromatic group and at least one ofAr¹ and Ar² bears a cross-linkable functional group; R¹, R², R³ and R⁴are independently alkyl, aralkyl or aryl with up to 20 carbon atoms; andq is at least
 1. 44. A cured polycondensate prepared by curing apolycondensate according to claim
 28. 45. A method of preparing a curedpolycondensate including the step of treating a polycondensate accordingto claim 28 with a curing agent.
 46. A method according to claim 45wherein the curing agent is light and a photoinitiator selected from thegroup consisting of 1-hydroxycyclohexylphenyl ketone, benzophenone,2-chlorothioxanthone, 2-methylthioxanthone, 2-iso-propylthioxanthone,benzoin, 4,4′-dimethoxybenzoin, camphorquinone and mixtures thereof isadded.
 47. A method according to claim 45 wherein an initiator selectedfrom dibenzoyl peroxide, t-butyl perbenzoate and azobisisobutyronitrileis added.